## anonymous one year ago Write the series in summation notation: 100 + 95 + 90 + 85 + 80

Let $S=100+95+90+85+80=5(20+19+18+17+16)$ $\therefore S=5(16+17+18+19+20)$ The sum of the terms in the bracket can be written using a summation $S=5\sum_{i=16}^{20}i$